Seed crystal holding chucks



United States Patent cc 3,046,029 SEED CRYSTAL HOLDING CHUCKS Joseph R.Weber, Chicago, and Svend E. Hauritz, Deerfield, Ill., assignors toHoffman Electronics Corporation, a corporation of California Filed Aug.7, 1959, Ser. No. 832,379 2 Claims. (Cl. 279-37) The present inventionrelates to mechanical chucks, and more particularly to chucks able toalign the axis of the object being held relative to the axis of thechuck and the shaft which supports the chuck.

In growing crystals, particularly of semiconductor materials such assilicon, it is the practice to dip a single crystal seed of the materialinto a crucible containing similar material in a molten state. The seedis rotated and with drawn slowly to produce a large single crystal fromthe molten mass. In the past the seed crystal has been secured to therotating shaft by a molybdenum wire. If the seed has any shapeimperfections it may be supported off the axis of the supporting shaftand upon rotation of that shaft the seed will execute an eccentricmotion with a resulting production of a defective crystal or none atall.

Therefore, it is an object of this invention to provide improvedsupporting means for a seed crystal in crystal growing apparatus.

It is a further object of the present invention to provide a novelseed-holding chuck.

It is another object of the present invention to provide a seed-holdingchuck that can position the object being held in axial alignment withthe shaft supporting the chuck.

According to one embodiment of the present invention, a chuck isconstructed so that as its jaws, which are pivotally connected, approacheach other, a clamp that is pivotally connected to one of the jawsengages the object to be held in the chuck and pivots to press theobject against the opposing jaw. A sleeve is adapted to slide over thejaws and press them tightly towards each other so that the axis of theobject is maintained coaxial with the axis of the chuck and the shaftwhich supports the chuck.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The presentinvention, both as to its organization and manner of operation, togetherwith further objects and advantages thereof, may best be understood byreference to the following description, taken in connection with theaccompanying drawings, in which,

FIGURE 1 is a cross sectional view of a chuck accord ing to the presentinvention.

FIGURE 2 is a cross sectional view taken along line 2-2 of FIGURE 1.

FIGURE 3 is a cross sectional view taken along line 3--3 of FIGURE 1.

Referring now to the drawings, FIGURE 1 shows jaws 11 and 12 pivotallysuspended from lift rod 13 by pins 14. The lower extremity of jaw 11contains guide pin 15 in hole 16. The lower extremity of jaw 12 containsclamp 21 pivotally connected to jaw 12 in opening 22 by pin 23. Sleeve24 slidably engages lift rod 13 and jaws 11 and 12. The lower extremityof the inner surface of sleeve 24 is tapered so as to mate slidably withthe upper extremity of the outer surfaces of jaws 11 and 12. The upperextremity of the inner surface of sleeve 24 is cylindrically shaped tomate with cylindrical lift rod 13 in slidable relationship. Crystalgrowing seed 31 contains a notch 32 circumscribed about each of its fourcorners. The lower end of seed 31 is inserted in silicon melt 33contained in crucible 34.

FIGURE 2 shows the configuration of jaws 11 and 12 by means of a crosssectional view. Seed 31 is held im- Federated July 24, 1962 mobilebetween jaw 11 and clamp 21, which pivots about pin 23 until it isaligned with seed 31.

FIGURE 3 shows the mating relationship between sleeve 24 and jaws 11 and12 by means of a cross sectional view. The operation of the chuck shownin FIG- URES 1, 2 and 3 will now be described.

Sleeve 24 is slid up along lift rod 13 so as to enable jaws 11 and 12 tobe spread apart by pivoting them in opposite directions about pins 14.Seed 31 is inserted between jaws 11 and 12 so that notch 32 is alignedwith guide pin 15. The lower extremities of jaws 11 and 12 are thenpressed towards each other until seed 31 is held securely between jaw 11and clamp 21. Clamp 21 pivots about pin 23 to engage seed 31 and topress it against jaw 11. Guide pin 15 helps to prevent vertical movementbetween seed 31 and jaws 11 and 12. Sleeve 24 is then slid down lift rod13 and along jaws 11 and 12, pressing jaws 11 and 12 towards each other,until seed 31 is held tightly. The entire apparatus can then be lowereduntil seed 31 is inserted into melt 33 in crucible 34. Lift rod 13 andcrucible 34 are slowly rotated in opposite directions. Lift rod 13 isthen very slowly and steadily raised vertically while rotating. Sleeve24 prevents lateral movement of jaws 11 and 12 with respect to lift rod13, and since the parts of the chuck are symmetrical, the axis of seed31 is coaxial with the axis of lift rod 13, and seed 31 does not wobble.As seed 31 slowly rises vertically, melt 33 continues to solidify in theregion of seed 31. This process is continued until a large singlecrystal of silicon has been lifted out of melt 33. If desired, crucible34 can be lowered instead of lift rod 13 being raised.

While particular embodiments of the present invention have been shownand described, it will be obvious to those skilled in the art thatchanges and modifications may be made without departing from thisinvention in its broader aspects, and, therefore, the aim in theappended claims is to cover all such changes and modifications as fallwithin the true spirit and scope of this invention.

We claim:

1. A seed holding chuck for drawing a polygonal crystal vertically outof a melt, comprising a lift means having a vertical axis, a pluralityof elongate vertical gripping jaws for grasping a seed crystal, meanspivotally mounting the upper end of each of said gripping jaws upon saidlift means, the outer surface of each of said gripping jaws beingtapered at the end which is pivoted to said lift means, and the innersurface of the lower end of each of said jaws being profiled for firmengagement with the corners of the seed crystal through a substantiallengthwise extent thereof to position the crystal in accurate alignmentwith said vertical axis; and a sleeve mounted for sliding movement alongsaid lift means and over the tapered ends of said gripping jaws wherebysaid gripping jaws are brought together to grip the corners of a crystalfirmly therebetween as said sleeve is moved towards the free ends ofsaid gripping jaws; the free end of one of said gripping jaws beingprovided with a cutout portion, and a clamp pivotally mounted in saidcutout portion, said clamp having a surface for crystal-grippingcooperation with the inner surface of another one of said other grippingjaws.

2. A chuck as set forth in claim 1, in which one of said gripping jawsis provided with a protruding pin for aligning said gripping jaws with anotch in the crystal held between said jaws.

References Cited in the file of this patent UNITED STATES PATENTS662,905 Banan Dec. 4, 1900 820,073 Spanogle May 8, 1906 1,575,149 Craiget al. Mar. 2, 1926 2,081,142 Branarnan May 25, 1937

